Even if it's not RMTers who are building subs, it doesn't detract from the point that houses are being hoarded in the tens or even hundreds by one single player account (40 FC houses * 4 regions = 160 FC houses per account).

There are several hoarders who are just utilizing this method to get gil and this massive influx of gil can lead to market manipulation which hurts ordinary players, not to mention these houses end up being locked away from other players who want them for their intended use.